Obesity is a serious disease of humans. A person is clinically obese if he or she has excess adipose tissue. More particularly, for purposes of this application, a person is obese if the person's body mass index equals or exceeds 27 kg/m.sup.2 and the person has excess adipose tissue. In the medical arts, the quantity of adipose tissue that is "excessive" is not well defined; but certainly greater than 25% of body weight as fat in a male and greater than 30% of body weight as fat in a female would be excessive.
Obesity has a number of known and suspected etiologies. See A. Sclafani, "Animal Models of Obesity: Classification and Characterization," Int. J. Obesity 8, 491-508 (1984); G. A. Bray, "Classification and Evaluation of the Obesities," Med. Clin. N. Am. 73, 161-184 (1989).
There is a strong positive correlation of increased body weight with elevated serum levels of triglycerides (TG) and cholesterol (CHOL), including low-density-lipoprotein-associated cholesterol (LDL-CHOL). Thus, obesity, in its known forms, is often associated with elevated serum levels of these substances.
The prevalence of obesity is increasing worldwide. The prevalence in the US population remained essentially constant, at about 25%, from 1960 to 1980. The prevalence in the US population increased between 1980 and 1990 to more than 33% and continues to increase. About 90 million people in the US are obese today. Similar statistics prevail in the rest of the world.
Obesity, in people who have the disease, is associated with physical, psychological, and social problems. Complications of obesity include, among others, diabetes mellitus, hypertension, hyperlipoproteinemia, cardiac diseases (atherosclerotic disease, congestive heart failure), pulmonary diseases (sleep apnea, restrictive lung disease), cerebrovascular accidents, cancers (breast, uterus, colon, prostate), gall bladder disease (stones, infection), toxemia during pregnancy, risks during surgery (pneumonia, wound infection, thrombo-phlebitis), gout, decreased fertility, degenerative arthritis, and early mortality.
Psychological complications of obesity include poor self-image and poor body-image. These complications are due in part to the fact that obesity is socially disfavored.
The fact that obesity is socially disfavored also presents social problems for obese people. Among these is discrimination in jobs, education and marriage.
Clearly, there is a need for methods to treat or prevent obesity. Effective treatment or preventative methods likely vary among the obese depending on the etiology of the obesity which an individual has.
Thus, there is a need to understand further the various etiologies of obesity. Such understanding will lead to methods and compositions to effectively treat or prevent the disease.
Further understanding of the etiologies of obesity also will lead to reduction in the prevalence of the social stigma associated with the disease, as it will allow the public at large to understand better that obesity is a disease which might afflict anyone and from which people do not choose to suffer. Such understanding also will allow obese persons to be convinced that they are unwilling victims of a disease, to understand through various diagnostic tests based on understanding of etiologies of the disease what the underlying cause of their obesity is, and in some cases to learn how to effectively treat the disease. Reduction in the prevalence of the social stigma associated with obesity and increased understanding among the obese concerning the disease will diminish the psychological complications and social problems which affect obese persons because of the disease.
Still further, understanding of the etiologies underlying obesity and the corresponding recognition that obesity is a disease eventually will lead medical insurance companies, which now at least in the United States typically do not recognize the condition as a disease, to recognize it as such and reimburse persons for diagnosis and treatment of it in the same way that the companies now do so for conditions that have long been recognized as diseases.
There has been speculation that one etiology of obesity in humans might be viral. A. Sclafani, supra. However, there has been no convincing evidence to support this speculation. Heretofore no virus has been identified as a cause of the disease in humans.